The invention addresses a method of generating logic control units for railroad Station-based Vital Computer Apparatuses, i.e. in railroad station system control units comprising at least one vital computer which, on the basis of a control program operating in combination with a logic unit, sends state switching controls to so-called yard elements, i.e. devices that are designed to perform specific train circulation-related operations, such as signaling devices and/or railroad switches and/or track circuits, or the like, and receives state feedback and/or diagnostic signals from said yard elements, said logic unit being generated automatically by a program, on the basis of the surrounding conditions as defined by the station diagram, comprising the list of yard elements and the location thereof with respect to tracks, and by a state table, wherein state assuming and/or state switching rules are settled for said yard elements, with reference to state and/or to state switching of the other yard elements and/or to the proper management of railroad traffic, said logic unit being a network of circuits with components operating according to Boolean logic functions and appropriately structured in compliance with the station diagram and with the state table, or said logic control unit being a program which includes algorithms composed of Boolean logic functions, which operate like networks of Boolean logic circuits.
A method and a system of this type is known from the Italian Patent application ITGE94A000061.
Station systems generally include a central unit which generates controls for different yard elements, such as signals and/or switches and/or track circuits, or the like. In order to ensure that train can transit safely, these yard elements shall assume different states, such as a “track open” or a stop signal, or the switching of a railroad switch according to a certain logic, which accounts for the states or state switching of other yard elements which, when brought to or left in certain states, might cause collisions or dangerous situations, or even simply not meet the regulations of admitted train circulation operations.
Yard elements are generally provided with actuators which perform state switching operations and with control and/or monitoring and/or diagnostic devices which send signals about the current state and the functionality thereof, so that the station-based stationary apparatus, i.e. the central control unit may have all railroad traffic settings under control at all time. Therefore, a predetermined state switching control transmitted to a particular element generates a chain of state maintaining or switching controls to other yard elements according to well-defined rules. Hence, the central control unit not only has control output subunits to communicate with each of the different elements in a dedicated manner, both for sending controls and for receiving feedback, but shall also operate under a strict logic, which incorporates yard element state switching rules, in compliance with safety assurance operations. These networks may be, and actually have been, purely made of hardware, i.e. of networks of circuits connected to a plurality of hardware components designed to perform predetermined Boolean operations. Typically, in railroad applications, the components designed to perform Boolean operations consisted of relay connection circuits or logic integrated circuits specially designed and connected to generate controls outputs compatible with yard element state switching rules.
As computers were introduced in railroad applications, hardware logic units were progressively replaced by control and monitoring programs including sets of Boolean equations, which describe the behaviors of the individual hardware Boolean operators and form, when appropriately integrated in a logic control program, a hardware-equivalent virtual logic unit.
A central vital computer may include different standardized library procedures, e.g. drivers for generating state switching controls, programs for managing diagnostic, control and monitoring functions which incorporate control and monitoring structures and reproduce general safety regulated movement rules. However, these general management programs need to be specially customized based on the particular structure of the station system, i.e. of its yard elements, and on related state switching rules, the so-called state tables. To this end, each central unit needs a logic control program for relating control and monitoring operations to the surrounding conditions, as defined by the station system structure. These control logics cannot be prefabricated but are application-dependent, i.e. depend on the specific station system construction.
Control logics, composed of sets of Boolean equations, whose variables are given by the states of the different elements and by the state controls and diagnostic data thereof, are known to be generated by automatic systems, i.e. generation programs which generate the sets of Boolean equations that form the algorithms of station-specific control and monitoring logic programs by using state tables or state switching tables and the station system diagram as a knowledge or input base.
In prior art, the method provides the implementation of the control logic so obtained in the vital computer of the logic control and monitoring module, and a consequent functional check, by possibly editing the logic program when errors or state incompatibilities between yard elements occur. This functional check typically includes field tests, i.e. is performed when the control and monitoring unit is installed in the specific station system.
The check mode is relatively complex and time-consuming. Further, when the logic unit is not a software product, but is composed of a set of electronic components designed to perform Boolean functions, the implementation is even more difficult, because the circuit has to be constructed before checking the operation thereof.